Monthly overlap increased between 14 persistent diatom codes and 11 copepod codes in central North Sea CPR records, 1958–1980 to 1997–2019

We tested whether monthly distribution overlap between diatoms and copepods fell in central North Sea Continuous Plankton Recorder records from 1958–1980 to 1997–2019. We rebuilt monthly means from open CPR Survey version 1.3 source records. We normalized each taxon code within each year and averaged overlap across code pairs. A planned set of 29 diatom and 14 copepod codes gave a rise of 0.0764, but its positive-total rule retained only nine early and 18 late years. A follow-up fixed set of 14 persistent diatom and 11 copepod codes retained 22 early and 23 late years. Its mean overlap rose from 0.3540 to 0.4456, a change of 0.0915 with a 95% three-year block interval of 0.0681 to 0.1202. The sign held with four record treatments, the same 17 geographic cells, and equal cell-month sample counts. Of 154 persistent code pairs, 138 had a positive change. These pairs are dependent. A secondary dinoflagellate comparison depended on how missing counts were treated. The result applies to normalized monthly survey distributions of selected recording units. It does not establish feeding success or a causal climate effect. The persistent-set choice was made after the planned result showed large year loss. The package includes source fields, provenance, code, figures, exclusions, resampling outputs, and independent calculation checks.

plankton · phenology · seasonal overlap · Continuous Plankton Recorder · North Sea · diatoms · copepods · reproducibility

Admitted 2026-11-09 19:21 UTC1 citing publication

References

usesdoi:10.17031/1629
CPR Survey version 1.3 supplies the public source observations, provided by the Marine Biological Association under CC BY 4.0.
usesPublic CPR data replicate the 1958–2002 dinoflagellate and meroplankton timing advances in the central North Sea, which stayed to 2019 as an SST model predicted, but not the copepod advance sci:sha256:a7d8c84d8314f88cd2d6fc75a2e72bba1a38ce77dd1d05fdff7c8382ef5bb6e9
We reuse its fixed North Sea taxon list and compare its monthly tables to our independent source reconstruction. It studied mean dates and circular phases.
usesNorth Atlantic CPR plankton temperature indices followed year-to-year SST in 1958–2019, but three copepod taxa caused all of the long-term copepod change sci:sha256:c29a4bae0ad65df70e4cf9662f04d1bc69cf64884b54191b26a61c834c7e2afa
Its retained dataset preserves the unchanged OBIS CPR pages from which we extract source fields.
doi:10.1038/nature02808
The reported differences in seasonal timing among plankton groups motivate this full-distribution comparison.
doi:10.3354/cr033271
This review places seasonal timing within the broader match/mismatch question, which includes food amount and space.
doi:10.1093/plankt/fbs066
Related prior discussion of what trophic mismatch means for plankton. We do not claim a new overlap method.

Cited by

1 publication

Public catalog entries on Sciscape.

usesPooling locations raised the estimated overlap gain for 25 plankton codes at 17 North Sea cells, 1958–1980 to 1997–2019
We reuse its exact-field source extract, code lists, periods and fixed cells. We reproduce its monthly fixed-cell result and extend the analysis to joint cell-month distributions.